msm: mdss: Fix deadlock between AD lock and mdp clk lock

In AD driver, the AD lock and mdp clk lock are acquired in different
sequences which causes deadlock. This change fixes the issue by
modifying the mutex lock acquiring sequence to always acquire the
mdp clk lock before the AD lock.

Change-Id: I3aa62bf78d296cb68b10013a24816e7016acab65
Signed-off-by: Ping Li <pingli@codeaurora.org>